Page:A color notation (Munsell).djvu/32

26 a number) at the right, below the line. Thus R$5⁄10$ means (red), $(5)⁄(10)$ and will be found to represent the qualities of the pigment vermilion.

Hue, value, and chroma unite in every color sensation, but the child cannot grasp them all at once. Hue-difference appeals to him first, and he gains a permanent idea of five principal hues from the enamels of, learning to name, match, imitate, and finally write them by their initials: R (red), Y (yellow), G (green), B (blue), and P (purple). Intermediates formed by uniting successive pairs are also written by the joined initials, YR (yellow-red), GY (green-yellow), BG (blue-green), PB (purple-blue), and RP (red-purple).

(41) Ten differences of hue are as many as a child can render at the outset, yet in matching and imitating them he becomes aware of their light and dark quality, and learns to separate it from hue as value-difference. Middle colors, as implied by that name, stand midway between white and black,—that is, on the equator of the sphere,—so that a middle red will be written R$1⁄3$, suggesting the steps 6, 7, 8, and 9 which are above the equator, while steps 4, 3, 2, and 1 are below. It is well to show only three values of a color at first; for instance, the middle value contrasted with a light and a dark one. These are written R$1⁄3$, R$1⁄5$, R$1⁄7$. Soon he perceives and can imitate finer differences, and the red scale may be written entire, as R$1⁄1$, R$1⁄3$, R$1⁄3$, R$1⁄4$, R$1⁄5$, R$1⁄6$, R$1⁄7$, R$1⁄8$, R$1⁄9$, with black as 0 and white as 10.

(42) Chroma-difference is the third and most subtle color quality. The child is already unconsciously familiar with the middle chroma of red, having had the enamels of always